Organic polymeric materials such as plastics and resins and lubricating and mineral oil are subject to thermal, oxidative and photodegradation. A great variety of stabilizers are known in the art for stabilizing various substrates. Their effectiveness varies depending on the causes of degradation and the substrate stabilized. During the course of this work, it was discovered that stabilizers that are very effective long term antioxidants are relatively poor process stabilizers which require stabilization of the substrate against thermal degradation for a short time, but at a relatively high temperature. Many stabilizers are relatively incompatible with the substrates which causes problems during the life of a product and lessens the stabilizer's effectiveness. Some stabilizers are either too volatile or thermally or hydrolytically unstable to be practical as commercial stabilizers.
The phosphites of this invention possess an unusual combination of desirable properties as compared to the prior art phosphites which makes these compounds particularly effective and useful as stabilizers.
Phosphites are disclosed in a number of publications. U.S. Pat. No. 4,196,117 discloses biphenyl-cyclic phosphites wherein the phosphorus atom is substituted by O- or S-hydrocarbyl or a hydrocarbyl biphenyl cyclic phosphite group. Soviet Union patent nos. 378,389, 429,070 and 440,390 disclose the stabilization of various polymers with organic phosphites or mixtures including said phosphites wherein the phosphites are methylenebisphenyl cyclic phosphites. Additional 1,1'-biphenyl-2,2'-diyl phosphites are disclosed in Chemical Abstracts, 68, 12597s (1968); 73, 15657a (1970) and 75, 130242q (1971). These various compounds are indicated to be stabilizers of various polymers.
U.S. Pat. Nos. 4,318,845 and 4,374,219 pertain to alkanolamine phosphite esters which are effective as process stabilizers and as color stabilizers and which are resistant to hydrolysis. These phosphite esters do not contain a hindered amine moiety having a free hydroxyl group attached to the 1-N atom of the piperidine group.
The reaction of phosphorochlorodites with alkanolamines is described by P. A. Odorisio et al, Phosphorus and Sulfur, 19, 1 (1984).
U.S. Pat. No. 4,259,492 describes dioxaphosphepines having the phosphorus atom directly substituted by an amine nitrogen. Thus, these materials have a P--N bond and are not tertiary phosphites, but have two ester groups and a phosphorus amide group in the same molecule. This patent generically discloses such dioxaphosphepines having the P--N bond which also contain a hindered amine moiety elsewhere in the molecule, but not compounds having the 1-N atom of the piperidine moiety substituted by hydroxyl.
The instant compounds having a 1-hydroxy hindered amine moiety attached to the P atom of the phosphepin or phosphocin through an oxygen ester linkage are significantly more effective as process stabilizers and color improvers than the compounds of the prior art. The instant compounds additionally provide enhanced light stabilization to the polymer compositions containing said compounds.
The synthesis of various phosphites, phosphinites and phosphinamide structures each containing the 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl moiety have been reported. [M. Konieczny et al, Phosphorus 2, 241 (1973); ibid, Z. Naturforsch (b) 33, 1040 (1977); ibid, Synthesis 583 (1978); M. B. Neiman et al, Izv. Akad Nauk SSSR, Eng Ed 1965, 529; G. V. Roschenthaler et al, Phosphorus/Sulfur, 4, 373 (1978)]
None of these structures contained the cyclic dibenzodioxaphosphepin or dioxaphosphocin ring system. The reported structures were used as intermediates in the synthesis of selenium compounds or for theoretical academic purposes.